voltage MOSFET Switch w/ Fast Settle Time for Switching E-Field

I have a copper mesh (10cm x 10cm square) in a vacuum chamber connected to a BNC connector by a 24-cm-long copper wire. The goal is to switch the mesh voltage (referenced to ground) from 8 V to ~0 V quickly. (This will switch the electric field in the chamber, which is a control mechanism for our atomic physics experiments. ) It is ess

ential that roughly 500 ns after the switching starts, the signal settles to <10 mV (~<0. 1%). The mesh is floating; it is not terminated in the chamber. The MOSFET ( ZVN2110A-ND, N-Channel Enhancement Mode) is driven by a IRS2117PBF-ND driver, which outputs a 15 V positive pulse. The baseline of this trigger pulse floats on V_S, which is tied to V_LO by a small resistor. The mesh is connected to Point B. The output low-pass filter was an attempt at fixing the problem. All resistor values were determined experimentally (i. e. by initially using potentiometers). The result was hard-wired using a "dead-bug" style on a copper-clad board. Probe Details: To simulate the mesh, I soldered a 24 cm wire to a piece of copper-clad perf board and connected it to the circuit output (Point B). I probed the signal on the perf board with a Tektronix probe (500 MHz, 8. 0 pF, 10MOhm, 10x) into a Tektronix scope (TDS3012 100 MHz digital scope). Observations: It switches quickly enough (although I could speed it up by removing the filter), the ringing amplitude and duration is tolerable, but on the (essential) microsecond time-scale, there is a large "hump" and droop/sag of 20 mV (labeled in image by red line). This is unacceptably large and makes it impossible to do our experiments, which take place from the moment of switching until about 10 microseconds after switching. Details of Application: We use electric fields to tune atomic...